The present invention relates generally to a convertible trailer assembly that can be pushed or pulled. More specifically, the present invention relates to an improved trailer assembly that can be converted between pushed or pulled operation or a retrofit assembly for a stroller that allows its conversion between pushed or pulled operation and includes a linkage assembly to provide a smoother towing experience for the user.
There are a number of convertible trailer/stroller devices in the art configured to convert between human powered pushing operation and towing operation such as behind a bicycle. Such devices generally employ a chariot type arrangement for the load carrying portion and then a forward section is modular such that different components can be installed for towing the trailer behind a bike or allowing the stroller to be employed in a pushed fashion by a user who is walking or jogging. One problem with such convertible devices however is that there are often additional parts and components that must be removed and stored and often tools are required to make the conversion.
Further the ergonomics of multi-function conversion devices is often overlooked. When using such a device as a trailer for a bicycle it is towed. However when converted to a jogger or stroller the device is pushed. In part this is necessitated by the fact that should a traditional device be towed by a jogging user the motion is jerky and incompatible with jogging. When a user is walking, the trailer is constantly accelerating and decelerating. This corresponds with a person's gait. This type of motion causes the trailer to feel as though it is pushing and pulling behind you as it catches up and falls behind with every step. While jogging, the motion is smoother, but the hitch point on the back moves up and down.
For example, U.S. Pat. No. 4,848,780 provides a carriage for a jogger that affixes to a belt worn about a user's waist. Further it can be seen that it includes a three link linkage that allows freedom to absorb the runner's strides through a pushing and pulling motion within the linkages. Similarly, U.S. Pat. No. 5,265,891 provides a trailer that employs a harness that goes over the wearer's shoulders and around their chest. The attachment point includes a universal joint and a spring that attempts to buffer motion induced from the road as well as from the wearer's stride. Still further, U.S. Pat. No. 7,938,409 provides for a trailer tow that employs a universal ball joint to introduce flexibility and several degrees of freedom to the attachment point as well as a resilient, shock absorbing member. However, none of these systems address the real issue of the momentum and inertia of the movement of the trailer itself.
Therefore, there is a need for a trailer device that can universally serve as a bicycle or human towed trailer that has a smooth towing motion that is comfortable for both walking and jogging, and can further operate as a steerable three wheel pushed stroller or wagon. There is a further need for such a device that can be instantly converted without the need for adding or subtracting parts as required in prior art conversions.